Halide-containing organic persistent luminescent materials for environmental sensing applications

Abstract

This review presents a summary of the molecular design of halide-containing organic persistent luminescent materials, and their environmental sensing applications.

Efficient Persistent Luminescence from Cellulose–Halide Mixtures for Optical Encryption

“…Furthermore, the halide anions are rich in outer electrons, which may participate with hydroxyls in the cellulose clusters and promote electron transition. Among the halide ions, bromides enhanced the phosphorescence more effectively than chlorides (Figure S2b), probably because the outer electrons were less constrained than that in chlorides and may enhance spin–orbit coupling through the heavy-atom effect. − As a result, more triplet states were produced through ISC, leading to higher phosphorescence intensity. Although the iodide ion is even heavier than the bromide ion, it can be easily oxidized in air, limiting its application.…”

“…To stabilize the excited states, metal salts were doped in cellulose matrices to reduce the molecular vibration of polysaccharide chains through electrostatic interaction between metal ions and lone-pair electrons . Furthermore, halide salts could increase intersystem crossing (ISC) through the external heavy-atom effect − and significantly increase the phosphorescence quantum yield. This method for tuning the persistent luminescence of cellulose could be applied easily to printing encryption on cellulose-based paper.…”

Host to regulate the T1–S1and T1–S0processes of guest excitons in doped systems to control the TADF and RTP emissions

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] However, both room-temperature phosphorescence (RTP)-type afterglow materials and thermally activated delayed fluorescence (TADF)-type afterglow materials face the problem of homogenization and monotonicity of the luminescence phenomenon. [16][17][18][19][20][21][22][23] Designing materials with both TADF and RTP, and further regulating and combining the two emissions, is an effective strategy to enrich the luminescence phenomenon of materials. It is a prerequisite for the realization of afterglow materials that the excitons of the singlet state (S 1 ) reach the triplet state (T 1 ) through intersystem crossing (ISC), and then the T 1 excitons involve two continuous processes, one is to generate phosphorescence emission from T 1 to S 0 , and the other is to return to S 1 through reverse intersystem crossing (RISC) and finally generates delayed fluorescence emission.…”

Molecular Thermal Motion Modulated Room-Temperature Phosphorescence for Multilevel Encryption

“…Purely organic room-temperature phosphorescence (RTP) materials with long lifetime have been widely applied in various areas, such as organic optoelectronics, biomedicine, optical sensing, and data encryption [1,2]. Over the past decade, strategies including halogen bonding [3,4], chargetransfer mediation [5][6][7], molecular-orbital hybridization [8,9], crystal engineering [10][11][12][13][14], polymer-matrix assistance [15][16][17][18][19][20], and host-guest doping [21][22][23][24][25][26] have been utilized to boost intersystem crossing and diminish nonradiative decays to realize organic RTP.…”